The prior art auto-control pencils are designed to have different specifications and sizes for the different uses of the pencils. The user selects a desired one according to the usages. Thus, it is often that the users must prepare various pencils for uses. However this prior art way has the following disadvantages. The cost is high for preparing various pencils. Moreover the users must carry multiple pencils for use. It is inconvenient.
Furthermore, the prior art auto-control pencils have complicated structures. Thereby some problems are induced. The first one is that the prior art auto-control pencils are only suitable for one size of pen lead. Further it is installed to repair the pencils. Moreover some parts must be detached for installing the pen lead. The cost for the prior art auto-control pencil is high and the lifetime is short.
Thereby the prior art auto-control pencils are not practical and cost-effective and are necessary to be improved.